The invention relates to text messaging in a telecommunication system and, more particularly, to a method and apparatus for providing text messaging between mobile handsets and TD devices in a telecommunication system.
Telecommunication devices for the deaf (TDD) have been developed that allow deaf persons to communicate by text messaging through the public switched telephone network (PSTN). The most common type of TDD is a telecommunication device (TD) at which a user may type in text messages for transmission and read received messages on a screen printout. A TD is fixed in location and is intended for communication with other TDDs over a landline network in an interactive manner. TDs commonly communicate according to the Electronic Industry Association""s (EIA) xe2x80x9cTelecommunications Devices for the Deafxe2x80x9d PN-1663 Standard (PN-1663).
A TDD, operating according to the PN-1663 Standard, communicates through the PSTN by transmitting and receiving strings of 1s and 0s that are encoded as either Baudot or ASCII codes. For Baudot coding, a 1 is transmitted through the PSTN as a 1400 Hz signal and a 0 is transmitted as an 1800 Hz signal. For ASCII coding, an originating TDD transmits a 1 through the PSTN as a 1270 Hz signal and a 0 as a 1070 Hz signal, and an answering TDD transmits a 1 as a 2225 Hz signal and a 0 as a 2025 Hz signal.
Recent advances in communication technology have resulted in cellular systems and technology that free users from the typical restraints of conventional landline telephone use. These advances include small, lightweight, portable, wireless phones that may be carried and used to communicate anywhere cellular service is provided. Present wireless phones have the capacity to send and receive short-text messages through a short messaging service (SMS). The SMS is standardized according to the standard in which the system operates. Unlike TDD systems using TD devices, SMS systems do not operate interactively over a circuit connection between communicating devices. SMS systems operate according to a store-and-deliver service, and SMS text messages have a fixed character length.
The present invention provides a method and apparatus for providing text messaging between mobile handsets and telecommunication devices in a telecommunication system. The method and apparatus allows short messaging service (SMS) capable mobile handsets to communicate with a telecommunication device (TD). The method and apparatus may be implemented into a mobile network/public switched telephone network (PSTN) as a stand-alone gateway interface without the need to reconfigure or modify the network hardware. A user of an SMS-capable mobile handset may send text messages to a user of a TD device or receive text messages sent by the user of a TD device. The method provides an interface function that allows a deaf person having access to a TD device to communicate with mobile handset users. It also allows a mobile handset user to send communications to a deaf person using a TD device.
The method and apparatus utilizes a gateway interface between the public switched telephone system (PSTN) and cellular network. The gateway interface provides a conversion function between the SMS text messaging protocol and TD device text messaging protocol. The conversion function includes appropriate queuing and timing features that allow the SMS and TD functions to communicate.
In an embodiment of the invention, the method and apparatus is implemented as a stand-alone gateway. The gateway may be implemented anywhere there is access to the public switched telephone network (PSTN) and coverage by a cellular system having short messaging service (SMS) capability. The gateway includes a controller and a transceiver. The controller may be implemented in a personal or similar type of computer. The transceiver operates according to the standard of a cellular system, including the system""s SMS features covering the area in which the transmitter is located. The transceiver is assigned a mobile network phone number and is capable of making and receiving calls under the control of the controller. The transceiver may be a conventional cellular handset connected to the controller through, for example, a bus such as an RS-232, or the transceiver may be a specially constructed transceiver built into the controller. The controller may be connected to the PSTN through a TD modem. The controller is assigned a PSTN phone number and communicates with TD devices that are connected to the PSTN using a TDD protocol. Connections may be provided through the Internet to allow multiple gateways to communicate with one another. The Internet connections allow multiple gateways to bypass the PSTN when communicating.
In order to initiate TD to mobile station communications, the user of a TD device dials the PSTN phone number that is assigned to the gateway. When a connection is made, the gateway then sends the appropriate responses in TDD protocol to prompt the user of the TD to enter the phone number of the mobile station(s) that are to receive a message. As the message is entered at the TD, the gateway buffers and converts the message to an appropriate format for SMS, according to the embodiment. By entering the message and following the prompts, the user is able to have the message sent to a destination mobile through the gateway.
In order to initiate mobile station to TD communications, the user of a mobile station sends a message via SMS to the mobile network phone number of the gateway transceiver. The message includes a phone number for each TD device that is to receive the message. Messages received by the gateway that are intended for a TD are placed in a queue within the gateway. The gateway processes the messages in the queue by dialing the phone number(s) of the message that has been in the queue the longest time. For each TD phone number that is busy, the gateway will retry dialing for a predetermined period of time. If the TD phone number is busy, the gateway will send an SMS message informing the mobile station that the TD is busy, but that the gateway will retry for the predetermined period of time. If the TD answers, the gateway performs appropriate functions so that the message sent to the TD meets TTD protocol requirements.